Method of protecting metal with amines and composition therefor



Oct. 16, 1956 y L. o. GUNDERSON ETAL 2,767,106

METHOD OF PROTECTING METAL WITH AMINES AND COMPOSITION THEREFOR FiledSept. 2'7, 1955 GLYCOLIC ALIPHATIC ACID AMINE VALIPHATIC mama 'GLYCOLATE WATER mun: AQUEOUS ALIPHATIC mama GLYOOLATE CV) METERING VALVEMETHOD OF PROTECTING IVETAL WITH AMINES AND COMPOSITION THEREFOR Lewis0. Gunderson, Morton Grove, and Wayne L. Denman,;ak Park, Ill, assignorsto Dearhorn Chemicai Company, Chicago, 111., a corporation of IilinoisApplication September 27, 1955, Serial No. 587,036

14 Claims. (Cl. 117-97) The instant invention relates to aliphatic aminematerials for water treating and processes of feeding such materials towater and effecting corrosion inhibition by their use in water systemsor aqueous media.

In particular, the invention relates to a method of protecting thesurfaces of metal pipe lines and apparatus in contact with transportedaqueous media having corrosystems, evaporator systems, processing watersystems, a

wet pipe fire systems, cooling water systems, etc.

In U. S. Patent No. 2, 460,259, issued to Kahler, there is described acorrosion inhibiting method using high molecular weight amines, aminesalts or amine oxides.

In U. S. Patent No. 2,712,531, issued to Maguire, there are describedcorrosion inhibiting compositions and methods involving the use of ablend of octadecyl amine and octadecyl amine acetate.

The instant invention is based upon the discovery that an aliphaticamine salt, not heretofore considered by or suggested by the workers inthe art as useful in this field, has uniquely superior properties whenused alone or in combination with an aliphatic amine for thepurpose ofinhibiting corrosion in aqueous mediaexposed to metal surfaces. Thespecific aliphaticamine saltemployed in the practice of the instantinventionis' the'glycolate and this salt is unique in its corrisioninhibiting properties and also in its greater solubility ordispersibility in aqueous media.

It is, therefore, an important object of the instant invention toprovide an improved method of eifecting corrosion inhibition of metalsurfaces exposed to aqueous media and an improved composition for suchuse.

It is a further object of the instant invention to provide an improvedcompositionand method of feeding the sameinto a flowing aqueous mediafor effecting corrosion inhibition of metal surfaces exposed thereto.

Other and further objects, features and advantages of the presentinvention will become apparent to those skilled in the art from thefollowing..detailed disclosure thereof and the drawing attached heretoand made a part hereof.

The invention consists in a method of protectingmetal contactingsurfaces in a continuously flowing system for transporting aqueous mediahaving corrosive qualities, which comprises the step of adding to thetransporting media an aliphatic amine glycolate wherein each aliphaticradical is a C12-C2o hydrocarbon radical, in concentrations of not morethan 100 p. p. m. but sufficient for forming a protective film on thesurfaces, and conveying the media sufiiciently to allow the film toform.

Patented Oct. 16, 1956 As shown in the drawing, which is essentiallydiagrammatic, aliphatic amine and glycolic acid are first reacted toobtain aliphatic amine glycolate. Water is added to obtain about a 1%solution which is fed through a metering valve into an aqueous systemwhere it performs its corrosion inhibiting function.

Another aspect of the instant invention comprises using the aliphaticamine glycolate in combination with an aliphatic amine; and stillanother aspect of the instant invention involves the use of an aliphaticamine in combination with an aliphatic amine glycolate and aliphaticamine acetate.

The aliphatic amine glycolate which may be used in the practice of theinstant invention is preferably .derived from a primary n-alkyl aminewherein'the alkyl radical is C12-C2o alkyl radical (or contains from 12to 20 carbon atoms). Such aliphatic amine salts include lauryl(dodecyl), myristyl (tetradecyl), cetyl (hexadecyl), stearyl(octadecyl), oleyl, eicosyl (C20) amine glycolates. The preferred aminesalt is octadecyl amine glycolate; and the preferred amine for use incombination therewith is octadecyl amine, but it will be appreciatedthat any of the aforementioned amines may be employed in the practice ofthe instant invention.

Heretofore, considerable difiiculties were encountered in using theknown aliphatic amine materials for corrosion inhibition particularlybecause of the ditficulty in handling these materials. First of all,only very minute amounts should be added to the aqueous medium involvedor the use of the aliphatic amine materials would not be practical.Secondly, these materials were found to be substantially insoluble inwater and very ditficult 'to disperse therein. In the Maguire patent, itis pointed out that octadecyl amine is extremely diflicult to dispersein water and thus. very difiicult to adequately feed into the system;whereas octadecyl amine acetate is more readily dispersed in Water, butit is per se strongly acidic so that corrosion may be caused at thepoint of injection of octadecyl amine acetate into an aqueous system. Aswill be appreciated, the aliphatic amine material must be prepared in adispersion or solution of something in the neighborhood of 1%concentration (perhaps within the range of 0.1 to 5% concentration) andthis dispersion is then fed into the aqueous medium so as to maintain aconcentration therein that is relatively minute, in the neighborhood of1 or 2 p. p. m. (parts per million). It is important to maintain areasonably great concentration of the aliphatic amine material in thedispersion feed .tank and increased dispersibility or solubility is ofparticular importance for this reason, even though the instant materialswill be ultimately employed in extremely dilute concentrations in theaqueous medium.

One aspect of the instant invention is based upon the discovery thatoctadecyl amine glycolate is more readily soluble or dispersible thanoctadecyl amine acetate. In addition, it exhibits better corrosioninhibiting properties when used in the practice of the instantinvention. Further, octadecyl amine glycolate (with or without octadecylamine) is capable of preparation into a dispersion adequate for feedinginto an aqueous system which dispersion contains a greater amount ofaliphatic amine material than can be put into a stable dispersion usingoctadecyl amine acetate. Corresponding results are obtained usingcorresponding aliphatic amine and aliphatic amine glycolates, as hereindescribed.

As a demonstration in the instant invention, 1 mol of technical gradeoctadecyl amine was melted and heated to about F. A charge of 0.5 mol of70% aqueous glycolic acid was slowly added with agitation to the meltedamine; and it was observed that a gelatinous product, insoluble in themolten amine, was first formed (and this product appears to be a waterdispersion of amine glycolate). By heating the mixture to about 250260F. the water was liberated and the mixture gradually became homogeneous.The homogeneous melt or blend so obtained was cooled with agitationuntil solidification occurred in order to obtain a homogeneous solidproduct. A 1% solution of the product in distilled water was prepared byadding 1 part by weight of the solid to 99 parts by weight of distilledwater and heating the solution to near the boiling point of water.Complete dispersion takes place after moderate stirring and a stableproduct results showing no signs of separation. The pH of this 1%solution was found to be 6.3. g

It was found that the instant dispersion is much more stable than acorresponding dispersion of 50% acetic acid neutralized octadecyl amine.Also, dispersions at concentrations which may be employed for actualcorrosion inhibition, such as dispersions ranging from 1 p. p. m. to 100or even 500 p. p. m. are extremely stable. In an actual corrosioninhibition test, a circulating water system with metallic parts thereinadapted to indicate rapidly the extent of corrosion is provided and the1% solution is metered slowly into the aqueous system so as to maintaina concentration therein of about 2 p. p. m. At first, of course,corrosion continues to take place because some time is required for thefilm to form. The rate of corrosion decreases, however, untilsubstantially no corrosion is obtained after twelve days of operation.This is an indication of excellent corrosion inhibition properties. Forexample, a corresponding treatment of the water with 50% acetic acidneutralized octadecyl amine requires a substantially longer period oftime before substantially 100% corrosion inhibition is effected. Inaddition to the superior dispersibility and/or solubility of theglycolate salt, and its superior function as a corrosion inhibitor inthe dilute concentrations employed in commercial use (i. e. from meretrace amounts of 0.5 p. p. m. to appreciable amounts such as 100 p. p.m.), the instant glycolate salt combinations thereof with the amine showdistinct reduction in corrosion at the point of injection into the watersystem. As previously mentioned, for commercial purposes the aliphaticamine material should not be used (as a practical matter) inconcentrations of more than 100 p. p. m., although the concentrationshould be sufficient to form a protective film on the metal surfaces,and such concentration may easily be as low as trace amounts or smallamounts such as 2 p. p. m.

If the foregoing procedure is employed except that 0.2 mol of glycolicacid is used instead of 0.5 mol, the resulting procedure givessubstantially the same results, except that the pH of a 1% solution is6.7. The superior corrosion inhibition properties exhibited in theprevious demonstration are comparable and the 1% solution, having a pHcloser to neutral, has even less corrosive properties per se.

If the procedure is again repeated, this time using 1 mol of glycolicacid, the resulting glycolate salt possesses superior corrosioninhibition properties when employed in the aqueous test system. The pHof a 1% solution is 4.7, but this solution does not exhibit thecorrosive properties of a corresponding acetate salt solution, and it isnoted that the completely neutralized glycolate solution is somewhatthicker than partially neutralized ones although it is extremely stableshowing no signs of separation (indicating perhaps a gel-like behavior).

if the foregoing procedure is again repeated except that 0.9 mol ofglycolic acid is used to react with the 1 mol of octadecyl amine, thesuperior stability of dispersions is again noticed and a 1% solution ofthe resulting blend has a pH of 5.2. Although this material exhibits thesuperior corrosion inhibition properties typical of the instantinvention, it has been found that it is preferable to employ aliphaticamine materials whose 1% solutions have a pH of 6 or more, which iscomparable to about octadecyl amine.

a 60-70% glycolic acid neutralized aliphatic amine. Blends containing aslittle as 10 or 20% aliphatic amine and -90% aliphatic amine glycolatepossess certain advantageous properties over the neutralized glycolatesalt; but the greatest advantages are obtained in the case of aliphaticamine materials whose 1% solution has a pH of 6 or more. In fact, the100% neutralized aliphatic amine glycolate per se has superior corrosioninhibition properties in the dilute concentrations employed commercially(i. e. not more than 100 p. p. m.) and this material has much less of atendency to cause corrosion at the point of injection into the systemthan does the corresponding acetate salt.

It has further been found that the glycolate may be used in combinationwith the acetate (as the salt component of an aliphatic amine material)to distinct advantage in the practice of the instant invention.Preferably the aliphatic amine salt is at least 50% glycolate, althoughas much as 75% acetate with the remainder glycolate may be used toadvantage.

For example, repeating the procedure hereinbefore described using 0.1mol of glycolic acid and 0.1 mol of acetic acid per mol of octadecylamine, it will be found that a product having good corrosion inhibitingproperties is obtained and this blend in a 1% solution has a pH of 6.8and may be readily dispersed in aqueous media for purposes of meteringinto the water system. Using, instead, 0.25 mol of glycolic acid and0.25 mol of acetic acid, one obtains a blend whose 1% aqueous solutionhas a pH of 6.4. This material has been found to be preferred for use inthe invention if it is desired to incorporate an acetate component inthe salt. Such a com position comprises 1 part (by weight) octadecylamine glycolate, 1 part octadecyl amine acetate, and 2 parts In general,the salt component (employing both glycolate and acetate) should be usedin the same proportions as those hereinbefore set forth for the use ofthe glycolate alone as the only salt component; and it is generallypreferable to employ a salt component equal in weight to aminecomponent. The amount of acetate may range from 0% to as much as 75% ofthe salt component, but if it is desired to employ the acetate salt foreconomic reasons or to obtain some special advantage therefrom, itshould be employed in a minimum amount of about 10% of the saltcomponent (the maximum being, of course, 75%

Again repeating the procedure using 0.45 mol of glycolic acid and 0.45mol of acetic acid (per mol of octadecyl amine) it will be found that a1% aqueous solution'of the resulting blend has a pH of 5.3 and thissolution possesses the characteristic high stability and superiorcorrosion inhibition properties of the invention.

In general, it is understood that these aliphatic amine materials form athin (mono-molecular) film on the metal surface. Any metal surface maybe thus protected, but low carbon steel is preferred as the structuralmaterial for water systems which must be protected (and the test metalpieces in the foregoing demonstrations included such steel) and thismetal is afforded excellent protection. The water used in the systemsprotected by the invention (and in the previous demonstrations) containsthe usual amounts of dissolved oxygen and carbon dioxide, which arebelieved to be the main corrosion inducing factors in the aqueous mediausually employed in water systems. Such Water systems often containwater having acid characteristics (pH 5.5 to 6.5), but the pH maysometimes reach a value of 8 (but ordinarily no higher).

In addition, it should be noted that the instant glycolates improvedropwise condensation of steam and thereby increase the heat transfercoetficient in heat exchange equipment, etc. a

It will be understood that modifications and variations may be effectedwithout departing from the spirit and scope of the novel concepts of thepresent invention.

I claim as my invention:

1. A method of protecting metal contacting surfaces in a continuouslyflowing system for transporting aqueous media having corrosivequalities, which comprises the stepof adding to the transporting mediaan aliphatic amine glycolate wherein each aliphatic radical is a C12-C20 hydrocarbon radical, in concentrations of not more than 100 p. p. m.but sufficient for forming a protective film on the surfaces, andconveying the media sufliciently to allow the film to form.

2. A method of protecting metal contacting surfaces in a continuouslyflowing system for transporting aqueous media having corrosivequalities, which comprises the step of adding to the transporting mediaoctadecyl amine glycolate, in concentrations of not more than 100 p. p.m. but suflicient for forming a protectivefilm on the surfaces, andconveying the media sufficiently to allow the film to form.

3. A method of protecting metal contacting surfaces in a continuouslyflowing system for transporting aqueous media having corrosivequalities, which comprises the step of adding to the transporting mediaa composition comprising -80% of an aliphatic amine and 90-20% of analiphatic amine glycolate wherein each aliphatic radical is a C12-C2ohydrocarbon radical, in concentrations of not more than 100 p. p. m. butsutficient for forming a protective film on the surfaces, and conveyingthe media sufiiciently to allow the film to form.

4. A method of protecting metal contacting surfaces in a continuouslyflowing system for transporting aqueous media having corrosivequalities, which comprises the step of adding to the transporting mediaan aliphatic amine salt which is 10%75% aliphatic amine acetate with theremainder aliphatic amine glycolate, wherein each of said aliphaticradicals is a C12-C20 hydrocarbon radical, in concentrations of not morethan 100 p. p. m. but sufficient for forming a protective film on thesurfaces, and conveying the media sufficiently to allow the film toform.'

5. A method of protecting metal contacting surfaces in a continuouslyflowing system for transporting aqueous media having corrosivequalities, which comprises the step of adding to the transporting mediaoctadecyl amine and octadecyl amine glycolate, in substantially equalproportions, in concentrations of not more than 100 p. p. m. butsufficient for forming a protective film on the surfaces, and conveyingthe media sufliciently to allow the film to form.

6. A method of protecting metal contacting surfaces in a continuouslyflowing system for transporting aqueous media having corrosivequalities, which comprises the step of adding to the transporting mediaa composition comprising 2 parts octadecyl amine, 1 part octadecyl amineglycolate and 1 part octadecyl amine acetate.

7. A method of feeding aliphatic amine material to water, whichcomprises first blending an aliphatic amine and an aliphatic amineglycolate wherein each aliphatic radical is a Cro-Czo hydrocarbonradical, in proportions of 1080% of the amine to 90-20% of theglycolate, then dispersing the blend and feeding the blend into Water.

8. A method of feeding aliphatic amine material to water, whichcomprises first blending an aliphatic amine and an aliphatic amine saltwherein each aliphatic radical is a Clo-C20 hydrocarbon radical, inproportions of 1080% of the amine to 9020% of the salt, said saltconsisting of 1075% acetate and the remainder glycolate, then dispersingthe blend and feeding the blend into water.

9. A method of feeding aliphatic amine material to water, whichcomprises first blending octadecyl amine and octadecyl amine glycolate,in proportions of l080% of the amine to 9020% of the glycolate, thendispersing the blend and feeding the blend into Water.

10. A method of feeding aliphatic amine material to water, whichcomprises first blending octadecyl amine and octadecyl amine salt, inproportions of 10-80% of the amine to 9020% of the salt, said saltconsisting of 10- acetate and the remainder glycolate, then dispersingthe blend and feeding the blend into Water.

11. A water treating composition, comprising a blend of an aliphaticamine and an aliphatic amine glycolate wherein each aliphatic radical isa Clo-C20 hydrocarbon radical, in proportions of 10-80% of the amine to20- of the glycolate.

12. A water treating composition, comprising a blend of an aliphaticamine and an aliphatic amine salt wherein each aliphatic radical is aClo-C20 hydrocarbon radical, in proportions of 10-80% of the amine to2090% of the salt, said salt consisting of 1075% acetate and theremainder glycolate.

13. A water treating composition, comprising a blend of octadecyl amineand octadecyl amine glycolate, in proportions of 1080% of the amine to2090% of the glycolate.

14. A water treating composition, comprising a blend of octadecyl amineand octadecyl amine salt, in proportions of 1080% of the amine to 20-90%of the salt, said salt consisting of 1075% acetate and the remainderglycolate.

References Cited in the file of this patent UNITED STATES PATENTS

1. A METHOD OF PROTECTING METAL CONTACTING SURFACES IN A CONTINUOUSLYFLOWING SYSTEM FOR TRANSPORTING AQUEOUS MEDIA HAVING CORROSIVEQUALITIES, WHICH COMPRISES THE STEP OF ADDING TO THE TRANSPORTING MEDIAAN ALIPHATIC AMINE GLYCOLATE WHEREIN EACH ALIPHATIC RADICAL IS A C12C20HYDROCARBON RADICAL, IN CONCENTRATIONS OF NOT MORE THAN 100 P.P.M. BUTSUFFICIENT FOR FORMING A PROTECTIVE